[PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Stefan Liebler]

Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
are comparing the nanosecond fields with the statx result.  Unfortunately
on s390(31bit) those fields are always zero if old KABI with non-LFS
support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.

As suggested by Adhemerval this patch disables the nanosecond check for
s390(31bit).
---
 io/tst-stat.c                      |  7 +++++--
 support/Makefile                   |  1 +
 support/support.h                  |  3 +++
 support/support_stat_nanoseconds.c | 31 ++++++++++++++++++++++++++++++
 4 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 support/support_stat_nanoseconds.c

diff --git a/io/tst-stat.c b/io/tst-stat.c
index 445ac4176c..397d480ecc 100644
--- a/io/tst-stat.c
+++ b/io/tst-stat.c
@@ -91,9 +91,12 @@ do_test (void)
       TEST_COMPARE (stx.stx_blocks, st.st_blocks);
 
       TEST_COMPARE (stx.stx_ctime.tv_sec, st.st_ctim.tv_sec);
-      TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
       TEST_COMPARE (stx.stx_mtime.tv_sec, st.st_mtim.tv_sec);
-      TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
+      if (support_stat_nanoseconds ())
+	{
+	  TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
+	  TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
+	}
     }
 
   return 0;
diff --git a/support/Makefile b/support/Makefile
index fc9f4936a8..900e17f94f 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -71,6 +71,7 @@ libsupport-routines = \
   support_set_small_thread_stack_size \
   support_shared_allocate \
   support_small_stack_thread_attribute \
+  support_stat_nanoseconds \
   support_subprocess \
   support_test_compare_blob \
   support_test_compare_failure \
diff --git a/support/support.h b/support/support.h
index 2e477c9e7c..90f3ff9d1a 100644
--- a/support/support.h
+++ b/support/support.h
@@ -134,6 +134,9 @@ extern ssize_t support_copy_file_range (int, off64_t *, int, off64_t *,
    operations (such as fstatat or utimensat).  */
 extern bool support_path_support_time64 (const char *path);
 
+/* Return true if stat supports nanoseconds resolution.  */
+extern bool support_stat_nanoseconds (void);
+
 __END_DECLS
 
 #endif /* SUPPORT_H */
diff --git a/support/support_stat_nanoseconds.c b/support/support_stat_nanoseconds.c
new file mode 100644
index 0000000000..c0d5b2c3a9
--- /dev/null
+++ b/support/support_stat_nanoseconds.c
@@ -0,0 +1,31 @@
+/* Check if stat supports nanosecond resolution.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+
+bool
+support_stat_nanoseconds (void)
+{
+  /* s390 stat64 compat symbol does not support nanoseconds resolution
+     and it used on non-LFS [f,l]stat[at] implementations.  */
+#if defined __linux__ && !defined __s390x__ && defined __s390__
+  return false;
+#else
+  return true;
+#endif
+}
-- 
2.28.0

Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Joseph Myers]

On Wed, 17 Mar 2021, Stefan Liebler via Libc-alpha wrote:

> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
> are comparing the nanosecond fields with the statx result.  Unfortunately
> on s390(31bit) those fields are always zero if old KABI with non-LFS
> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.

My understanding is that, if using a kernel that supports statx, this 
disabling is not needed.

If so, we want to be sure to remove this disabling once we can assume a 
kernel supporting statx (on s390).  The way we ensure that is having a 
conditional on __ASSUME_STATX in the code in question so that it's 
immediately visible when we remove __ASSUME_STATX that this disabling can 
be removed from the glibc source code as well.

-- 
Joseph S. Myers
joseph@codesourcery.com

Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Adhemerval Zanella]

On 17/03/2021 18:01, Joseph Myers wrote:
> On Wed, 17 Mar 2021, Stefan Liebler via Libc-alpha wrote:
> 
>> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
>> are comparing the nanosecond fields with the statx result.  Unfortunately
>> on s390(31bit) those fields are always zero if old KABI with non-LFS
>> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.
> 
> My understanding is that, if using a kernel that supports statx, this 
> disabling is not needed.

The non-LFS stat does not call statx, so the nanoseconds call should be
disable only for non-LFS mode.

> 
> If so, we want to be sure to remove this disabling once we can assume a 
> kernel supporting statx (on s390).  The way we ensure that is having a 
> conditional on __ASSUME_STATX in the code in question so that it's 
> immediately visible when we remove __ASSUME_STATX that this disabling can 
> be removed from the glibc source code as well.
> 

Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Adhemerval Zanella]

On 17/03/2021 10:03, Stefan Liebler wrote:
> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
> are comparing the nanosecond fields with the statx result.  Unfortunately
> on s390(31bit) those fields are always zero if old KABI with non-LFS
> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.
> 
> As suggested by Adhemerval this patch disables the nanosecond check for
> s390(31bit).

LGTM, the fstatat call does not call statx and even for LFS that call statx
it might ended calling old stat syscall in the fallback part that does not

About the __ASSUME_STATX note Joseph has raised, I think we should add it
on Linux at least for fstatat64 implementation. However it does not really
help on the fstatat one.  I will try to spare some time to make fstatat.c
use statx as well, so we can tie the test to __ASSUME_STATX.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  io/tst-stat.c                      |  7 +++++--
>  support/Makefile                   |  1 +
>  support/support.h                  |  3 +++
>  support/support_stat_nanoseconds.c | 31 ++++++++++++++++++++++++++++++
>  4 files changed, 40 insertions(+), 2 deletions(-)
>  create mode 100644 support/support_stat_nanoseconds.c
> 
> diff --git a/io/tst-stat.c b/io/tst-stat.c
> index 445ac4176c..397d480ecc 100644
> --- a/io/tst-stat.c
> +++ b/io/tst-stat.c
> @@ -91,9 +91,12 @@ do_test (void)
>        TEST_COMPARE (stx.stx_blocks, st.st_blocks);
>  
>        TEST_COMPARE (stx.stx_ctime.tv_sec, st.st_ctim.tv_sec);
> -      TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
>        TEST_COMPARE (stx.stx_mtime.tv_sec, st.st_mtim.tv_sec);
> -      TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
> +      if (support_stat_nanoseconds ())
> +	{
> +	  TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
> +	  TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
> +	}
>      }
>  
>    return 0;
> diff --git a/support/Makefile b/support/Makefile
> index fc9f4936a8..900e17f94f 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -71,6 +71,7 @@ libsupport-routines = \
>    support_set_small_thread_stack_size \
>    support_shared_allocate \
>    support_small_stack_thread_attribute \
> +  support_stat_nanoseconds \
>    support_subprocess \
>    support_test_compare_blob \
>    support_test_compare_failure \
> diff --git a/support/support.h b/support/support.h
> index 2e477c9e7c..90f3ff9d1a 100644
> --- a/support/support.h
> +++ b/support/support.h
> @@ -134,6 +134,9 @@ extern ssize_t support_copy_file_range (int, off64_t *, int, off64_t *,
>     operations (such as fstatat or utimensat).  */
>  extern bool support_path_support_time64 (const char *path);
>  
> +/* Return true if stat supports nanoseconds resolution.  */
> +extern bool support_stat_nanoseconds (void);
> +
>  __END_DECLS
>  
>  #endif /* SUPPORT_H */
> diff --git a/support/support_stat_nanoseconds.c b/support/support_stat_nanoseconds.c
> new file mode 100644
> index 0000000000..c0d5b2c3a9
> --- /dev/null
> +++ b/support/support_stat_nanoseconds.c
> @@ -0,0 +1,31 @@
> +/* Check if stat supports nanosecond resolution.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <stdbool.h>
> +
> +bool
> +support_stat_nanoseconds (void)
> +{
> +  /* s390 stat64 compat symbol does not support nanoseconds resolution
> +     and it used on non-LFS [f,l]stat[at] implementations.  */
> +#if defined __linux__ && !defined __s390x__ && defined __s390__
> +  return false;
> +#else
> +  return true;
> +#endif
> +}
> 

Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Stefan Liebler]

On 18/03/2021 14:31, Adhemerval Zanella wrote:
> 
> 
> On 17/03/2021 10:03, Stefan Liebler wrote:
>> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
>> are comparing the nanosecond fields with the statx result.  Unfortunately
>> on s390(31bit) those fields are always zero if old KABI with non-LFS
>> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.
>>
>> As suggested by Adhemerval this patch disables the nanosecond check for
>> s390(31bit).
> 
> LGTM, the fstatat call does not call statx and even for LFS that call statx
> it might ended calling old stat syscall in the fallback part that does not
> 
> About the __ASSUME_STATX note Joseph has raised, I think we should add it
> on Linux at least for fstatat64 implementation. However it does not really
> help on the fstatat one.  I will try to spare some time to make fstatat.c
> use statx as well, so we can tie the test to __ASSUME_STATX.
> 
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
> 

Hi Adhemerval,

Sorry for the delay, I was busy with another project.
Thanks for your series
"[PATCH 1/5] linux: Implement fstatat with __fstatat64_time64"
https://sourceware.org/pipermail/libc-alpha/2021-March/124191.html

As also mentioned there, with your series, at least on my s390 systems,
stat is then using statx and the nanosecond fields are not zero anymore.

Shall I commit my patch as is and as soon as you've commited your
series, you can adjust support_stat_nanoseconds to return false if
__ASSUME_STATX is not defined?

Thanks,
Stefan

Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Adhemerval Zanella]

On 23/03/2021 13:13, Stefan Liebler wrote:
> On 18/03/2021 14:31, Adhemerval Zanella wrote:
>>
>>
>> On 17/03/2021 10:03, Stefan Liebler wrote:
>>> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
>>> are comparing the nanosecond fields with the statx result.  Unfortunately
>>> on s390(31bit) those fields are always zero if old KABI with non-LFS
>>> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.
>>>
>>> As suggested by Adhemerval this patch disables the nanosecond check for
>>> s390(31bit).
>>
>> LGTM, the fstatat call does not call statx and even for LFS that call statx
>> it might ended calling old stat syscall in the fallback part that does not
>>
>> About the __ASSUME_STATX note Joseph has raised, I think we should add it
>> on Linux at least for fstatat64 implementation. However it does not really
>> help on the fstatat one.  I will try to spare some time to make fstatat.c
>> use statx as well, so we can tie the test to __ASSUME_STATX.
>>
>> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
>>
> 
> Hi Adhemerval,
> 
> Sorry for the delay, I was busy with another project.
> Thanks for your series
> "[PATCH 1/5] linux: Implement fstatat with __fstatat64_time64"
> https://sourceware.org/pipermail/libc-alpha/2021-March/124191.html
> 
> As also mentioned there, with your series, at least on my s390 systems,
> stat is then using statx and the nanosecond fields are not zero anymore.
> 
> Shall I commit my patch as is and as soon as you've commited your
> series, you can adjust support_stat_nanoseconds to return false if
> __ASSUME_STATX is not defined?

Yes, I can rebase on top your patch.  I think we still need to handle
the nanosecond missing support on older kernels.

Thanks for checking on s390, if you can review the patchset I would be
grateful

Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Stefan Liebler]

On 24/03/2021 18:40, Adhemerval Zanella wrote:
> 
> 
> On 23/03/2021 13:13, Stefan Liebler wrote:
>> On 18/03/2021 14:31, Adhemerval Zanella wrote:
>>>
>>>
>>> On 17/03/2021 10:03, Stefan Liebler wrote:
>>>> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
>>>> are comparing the nanosecond fields with the statx result.  Unfortunately
>>>> on s390(31bit) those fields are always zero if old KABI with non-LFS
>>>> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.
>>>>
>>>> As suggested by Adhemerval this patch disables the nanosecond check for
>>>> s390(31bit).
>>>
>>> LGTM, the fstatat call does not call statx and even for LFS that call statx
>>> it might ended calling old stat syscall in the fallback part that does not
>>>
>>> About the __ASSUME_STATX note Joseph has raised, I think we should add it
>>> on Linux at least for fstatat64 implementation. However it does not really
>>> help on the fstatat one.  I will try to spare some time to make fstatat.c
>>> use statx as well, so we can tie the test to __ASSUME_STATX.
>>>
>>> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
>>>
>>
>> Hi Adhemerval,
>>
>> Sorry for the delay, I was busy with another project.
>> Thanks for your series
>> "[PATCH 1/5] linux: Implement fstatat with __fstatat64_time64"
>> https://sourceware.org/pipermail/libc-alpha/2021-March/124191.html
>>
>> As also mentioned there, with your series, at least on my s390 systems,
>> stat is then using statx and the nanosecond fields are not zero anymore.
>>
>> Shall I commit my patch as is and as soon as you've commited your
>> series, you can adjust support_stat_nanoseconds to return false if
>> __ASSUME_STATX is not defined?
> 
> Yes, I can rebase on top your patch.  I think we still need to handle
> the nanosecond missing support on older kernels.
I've just committed this patch.
> 
> Thanks for checking on s390, if you can review the patchset I would be
> grateful
Sure. I've left some comments

Thanks,
Stefan